Heat a large skillet over medium heat. Add butter and melt. Add onions and apples, reduce heat to low, and let simmer for approximately 5 minutes or until onions and apples are tender. Add vinegar and cassis, and season with salt, pepper, and a dash of sugar. Simmer for 5 minutes and set aside.

Heat a medium or large skillet over medium-high heat. Season foie gras with salt and pepper, and then sear on both sides until cooked to desired degree of doneness. Remove foie gras to a towel to absorb excess fat. Add port to skillet and deglaze , stirring and scraping the bottom of the pan with a wooden spoon. Add the chopped black truffles and veal stock. Cook until reduced slightly and then adjust seasoning.

To plate, divide apple compote among 4 plates and then top with foie gras. Garnish with fried Italian parsley. Season with fleur de Sel and serve immediately.